1. Field of the Invention
The present invention relates to a sheet tray device for accommodating a media sheet such as paper sheet, OHP sheet, envelop and postal card, and also an image forming apparatus including such a sheet tray device.
2. Discussion of Related Art
It is common that a sheet tray device for use in an image forming apparatus is provided by a single tray member that is removably introduced into a main body of the image forming apparatus, as disclosed in JP-2005-314067A.
The sheet tray device is required to accommodate the media sheets of various sizes such as A4-sized papers and A-5 sized papers. However, the media sheets of plurality of different sizes can not be concurrently accommodated in the single tray member. Every time the size of the media sheets (on which an image forming or printing operation is to be performed) is changed to another size of those, the sheet tray device has to be removed from the main body of the image forming apparatus, for carrying out a sheet replacement operation, namely, for changing the media sheets with those of the other size.
That is, where the image forming operation is to be carried out on the media sheets of various sizes, the sheet replacement operation has to be frequently done. Since such a sheet replacement operation is generally cumbersome, the conventional image forming apparatus is poor in maneuverability, particularly, for a user who has to carry out the image forming operation on the media sheets of various sizes.
The above problem could be solved, for example, by employing an image forming apparatus such as large-sized copier machine equipped with a sheet tray device that has a plurality of trays for accommodating respective different sizes of media sheets. In the large-sized copier machine in which the media sheets of different sizes can be concurrently accommodated in the respective trays, the sheet replacement operation is not required every time the size of the media sheets is changed. However, the large-sized image forming apparatus is not feasible for a domestic use in which there is not a large space available for installation of the apparatus.
For solving the above problem, the present inventor manufactured, by way of trial, a double-deck sheet tray device including the conventional tray as a first tray for accommodating first size sheets, and a second tray for accommodating second size sheets whose size is smaller than that of the first size sheets, wherein the second tray is movably disposed on an upper side of the first tray. However, another problem is encountered in this double-deck sheet tray device. The problem is that refilling the first tray with the sheets could be made difficult by the arrangement in which the second tray is disposed to cover an upper opening of the first tray.
In view of this, in the double-deck sheet tray device manufactured by way of trial, the second tray is constituted by a support member and a supported body. The support member is arranged to bridge between opposite side walls of the first tray, while the supported body is supported by the support member and is pivotable to open and close the upper opening of the first tray. However, the double-deck sheet tray device suffers from still another problem that the second tray could be rotated relative to the first tray or removed from the first tray during movement of the second tray relative to the first tray.